The present invention relates to a medical apparatus having a distal curved configuration which avoids contact of the apparatus distal end with an introducer device. The present invention also relates to the field of electrosurgery, and more particularly to surgical devices and methods which employ high frequency electrical energy to treat tissue in regions of the spine. The present invention is particularly suited for the treatment of the discs, cartilage, ligaments, and other tissue within the vertebral column.
The major causes of persistent, often disabling, back pain are disruption of the disc annulus, chronic inflammation of the disc, contained and non-contained herniation, and relative instability of the vertebral bodies surrounding a given disc, such as the instability that often occurs due to a stretching of the interspinous tissue surrounding the vertebrae. Intervertebral discs mainly function to cushion and tether the vertebrae, while the interspinous tissue (i.e., tendons and cartilage, and the like) function to support the vertebrae so as to provide flexibility and stability to the patient""s spine.
Spinal discs comprise a central hydrophilic cushion, the nucleus pulposus, surrounded by a multi-layered fibrous ligament, the annulus fibrosus. As discs degenerate, they lose their water content and height, bringing the adjoining vertebrae closer together. This results in a weakening of the shock absorption properties of the disc and a narrowing of the nerve openings in the sides of the spine which may pinch these nerves. This disc degeneration can eventually cause back and leg pain. Weakness in the annulus from degenerative discs or disc injury can allow fragments of nucleus pulposus from within the disc space to migrate through the annulus fibrosus and into the spinal canal. There, displaced nucleus pulposus tissue, or protrusion of the annulus fibrosus, e.g., due to herniation, may impinge on spinal nerves or nerve roots. A weakening of the annulus fibrosus can cause the disc to bulge, e.g., a contained herniation, and the mere proximity of the nucleus pulposus or the damaged annulus to a nerve can cause direct pressure against the nerve, resulting in pain and sensory and motor deficit.
Often, inflammation from disc herniation can be treated successfully by non-surgical means, such as rest, therapeutic exercise, oral anti-inflammatory medications or epidural injection of corticosteroids. Such treatments result in a gradual but progressive improvement in symptoms and allow the patient to avoid surgical intervention.
In some cases, the disc tissue is irreparably damaged, thereby necessitating removal of a portion of the disc or the entire disc to eliminate the source of inflammation and pressure. In more severe cases, the adjacent vertebral bodies must be stabilized following excision of the disc material to avoid recurrence of the disabling back pain. One approach to stabilizing the vertebrae, termed spinal fusion, is to insert an interbody graft or implant into the space vacated by the degenerative disc. In this procedure, a small amount of bone may be grafted and packed into the implants. This allows the bone to grow through and around the implant, fusing the vertebral bodies and preventing reoccurrence of the symptoms.
Until recently, surgical spinal procedures resulted in major operations and traumatic dissection of muscle and bone removal or bone fusion. To overcome the disadvantages of traditional traumatic spine surgery, minimally invasive spine surgery was developed. In endoscopic spinal procedures, the spinal canal is not violated and therefore epidural bleeding with ensuing scarring is minimized or completely avoided. In addition, the risk of instability from ligament and bone removal is generally lower in endoscopic procedures than with open procedures. Further, more rapid rehabilitation facilitates faster recovery and return to work.
Minimally invasive techniques for the treatment of spinal diseases or disorders include chemonucleolysis, laser techniques, and mechanical techniques. These procedures generally require the surgeon to form a passage or operating corridor from the external surface of the patient to the spinal disc(s) for passage of surgical instruments, implants and the like. Typically, the formation of this operating corridor requires the removal of soft tissue, muscle or other types of tissue depending on the procedure (i.e., laparascopic, thoracoscopic, arthroscopic, back, etc.). This tissue is usually removed with mechanical instruments, such as pituitary rongeurs, curettes, graspers, cutters, drills, microdebriders and the like. Unfortunately, these mechanical instruments greatly lengthen and increase the complexity of the procedure. In addition, these instruments might sever blood vessels within this tissue, usually causing profuse bleeding that obstructs the surgeon""s view of the target site.
Once the operating corridor is established, the nerve root is retracted and a portion or all of the disc is removed with mechanical instruments, such as a pituitary rongeur. In addition to the above problems with mechanical instruments, there are serious concerns because these instruments are not precise, and it is often difficult, during the procedure, to differentiate between the target disc tissue, and other structures within the spine, such as bone, cartilage, ligaments, nerves and non-target tissue. Thus, the surgeon must be extremely careful to minimize damage to the cartilage and bone within the spine, and to avoid damaging nerves, such as the spinal nerves and the dura mater surrounding the spinal cord.
Lasers were initially considered ideal for spine surgery because lasers ablate or vaporize tissue with heat, which also acts to cauterize and seal the small blood vessels in the tissue. Unfortunately, lasers are both expensive and somewhat tedious to use in these procedures. Another disadvantage with lasers is the difficulty in judging the depth of tissue ablation. Since the surgeon generally points and shoots the laser without contacting the tissue, he or she does not receive any tactile feedback to judge how deeply the laser is cutting. Because healthy tissue, bones, ligaments and spinal nerves often lie within close proximity of the spinal disc, it is essential to maintain a minimum depth of tissue damage, which cannot always be ensured with a laser.
Monopolar and bipolar radiofrequency devices have been used in limited roles in spine surgery, such as to cauterize severed vessels to improve visualization. Monopolar devices, however, suffer from the disadvantage that the electric current will flow through undefined paths in the patient""s body, thereby increasing the risk of undesirable electrical stimulation to portions of the patient""s body. In addition, since the defined path through the patient""s body has a relatively high impedance (because of the large distance or resistivity of the patient""s body), large voltage differences must typically be applied between the return and active electrodes in order to generate a current suitable for ablation or cutting of the target tissue. This current, however, may inadvertently flow along body paths having less impedance than the defined electrical path, which will substantially increase the current flowing through these paths, possibly causing damage to or destroying surrounding tissue or neighboring peripheral nerves.
Other disadvantages of conventional RF devices, particularly monopolar devices, is nerve stimulation and interference with nerve monitoring equipment in the operating room. In addition, these devices typically operate by creating a voltage difference between the active electrode and the target tissue, causing an electrical arc to form across the physical gap between the electrode and tissue. At the point of contact of the electric arcs with tissue, rapid tissue heating occurs due to high current density between the electrode and tissue. This high current density causes cellular fluids to rapidly vaporize into steam, thereby producing a xe2x80x9ccutting effectxe2x80x9d along the pathway of localized tissue heating. Thus, the tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue site. This collateral tissue damage often causes indiscriminate destruction of tissue, resulting in the loss of the proper function of the tissue. In addition, the device does not remove any tissue directly, but rather depends on destroying a zone of tissue and allowing the body to eventually remove the destroyed tissue.
Many patients experience discogenic pain due to defects or disorders of intervertebral discs. Such disc defects include annular fissures, fragmentation of the nucleus pulposus, and contained herniation. A common cause of pain related to various disc disorders is compression of a nerve root by the disc. In many patients for whom major spinal surgery is not indicated, discogenic pain naturally diminishes in severity over an extended period of time, perhaps several months. There is a need for a minimally invasive method to treat such patients in order to alleviate the chronic, and often debilitating, pain associated with spinal nerve root compression. The instant invention provides methods for decompressing nerve roots by ablation of disc tissue at relatively low temperatures during a percutaneous procedure, wherein the volume of the disc is decreased and discogenic pain is alleviated.
The present invention provides systems, apparatus, and methods for selectively applying electrical energy to structures within a patient""s body, such as the intervertebral disc. The systems and methods of the present invention are useful for shrinkage, ablation, resection, aspiration, and/or hemostasis of tissue and other body structures in open and endoscopic spine surgery. In particular, the present invention includes a method and system for debulking, ablating, and shrinking the disc.
The present invention further relates to an electrosurgical probe including an elongated shaft having first and second curves in the distal end portion of the shaft, wherein the shaft can be rotated within an intervertebral disc to contact fresh tissue of the nucleus pulposus. The present invention also relates to an electrosurgical probe including an elongated shaft, wherein the shaft distal end can be guided to a specific target site within a disc, and the shaft distal end is adapted for localized ablation of targeted disc tissue. The present invention further relates to a probe having an elongated shaft, wherein the shaft includes an active electrode, an insulating collar, and an outer shield, and wherein the active electrode includes a head having an apical spike and a cusp. The present invention still further relates to a method for ablating disc tissue with an electrosurgical probe, wherein the probe includes an elongated shaft, and the shaft distal end is guided to a specific target site within a disc.
In one aspect, the present invention provides a method of treating a herniated intervertebral disc. The method comprises positioning at least one active electrode within the intervertebral disc. High frequency voltage is applied between the active electrode(s) and one or more return electrode(s) to debulk, ablate, coagulate and/or shrink at least a portion of the nucleus pulposus and/or annulus. The high frequency voltage effects a controlled depth of thermal heating to reduce the water content of the nucleus pulposus, thereby debulking the nucleus pulposus and reducing the internal pressure on the annulus fibrosus.
In an exemplary embodiment, an electrically conductive media, such as isotonic saline or an electrically conductive gel, is delivered to the target site within the intervertebral disc prior to delivery of the high frequency energy. The conductive media will typically fill the entire target region such that the active electrode(s) are submerged throughout the procedure. In other embodiments, the extracellular conductive fluid (e.g., the nucleus pulposus) in the patient""s disc may be used as a substitute for, or as a supplement to, the electrically conductive media that is applied or delivered to the target site. For example, in some embodiments, an initial amount of conductive media is provided to initiate the requisite conditions for ablation. After initiation, the conductive fluid already present in the patient""s tissue is used to sustain these conditions.
In another aspect, the present invention provides a method of treating a disc having a contained herniation or fissure. The method comprises introducing an electrosurgical instrument into the patient""s intervertebral disc either percutaneously or through an open procedure. The instrument is steered or otherwise guided into close proximity to the contained herniation or fissure and a high frequency voltage is applied between an active electrode and a return electrode so as to debulk the nucleus pulposus adjacent the contained herniation or fissure. In some embodiments a conductive fluid is delivered into the intervertebral disc prior to applying the high frequency voltage to ensure that sufficient conductive fluid exists for plasma formation and to conduct electric current between the active and return electrodes. Alternatively, the conductive fluid can be delivered to the target site during the procedure. The heating delivered through the electrically conductive fluid debulks the nucleus pulposus, and reduces the pressure on the annulus fibrosus so as to reduce the pressure on the affected nerve root and alleviate neck and back pain.
In another aspect, the present invention provides a method for treating degenerative intervertebral discs. The active electrode(s) are advanced into the target disc tissue in an ablation mode, where the high frequency voltage is sufficient to ablate or remove the nucleus pulposus through molecular dissociation or disintegration processes. In these embodiments, the high frequency voltage applied to the active electrode(s) is sufficient to vaporize an electrically conductive fluid (e.g., gel, saline and/or intracellular fluid) between the active electrode(s) and the tissue. Within the vaporized fluid, an ionized plasma is formed and charged particles (e.g., electrons) cause the molecular breakdown or disintegration of several cell layers of the nucleus pulposus. This molecular dissociation is accompanied by the volumetric removal of the tissue. This process can be precisely controlled to effect the volumetric removal of tissue as thin as 10 microns to 150 microns with minimal heating of, or damage to, surrounding or underlying tissue structures. A more complete description of this phenomenon is described in commonly assigned U.S. Pat. No. 5,697,882 the complete disclosure of which is incorporated herein by reference.
An apparatus according to the present invention generally includes a shaft having proximal and distal end portions, an active electrode at the distal end and one or more connectors for coupling the active electrode to a source of high frequency electrical energy. The probe or catheter may assume a wide variety of configurations, with the primary purpose being to introduce the electrode assembly into the patient""s disc (in an open or endoscopic procedure) and to permit the treating physician to manipulate the electrode assembly from a proximal end of the shaft. The probe shaft can be flexible, curved, or steerable so as to allow the treating physician to move the active electrode into close proximity of the region of the disc, e.g., herniation, to be treated. The electrode assembly includes one or more active electrode(s) and a return electrode spaced from the active electrode(s) either on the instrument shaft or separate from the instrument shaft.
The active electrode(s) may comprise a single active electrode, or an electrode array, extending from an electrically insulating support member, typically made of an inorganic material such as ceramic, silicone or glass. The active electrode will usually have a smaller exposed surface area than the return electrode, such that the current densities are much higher at the active electrode than at the return electrode. Preferably, the return electrode has a relatively large, smooth surface extending around the instrument shaft to reduce current densities, thereby minimizing damage to adjacent tissue.
In another aspect, the present invention provides a method of treating an intervertebral disc, the method comprising contacting at least a first region of the intervertebral disc with at least one active electrode of an electrosurgical system. The at least one active electrode may be disposed on the distal end portion of a shaft of the electrosurgical system. A first high frequency voltage is applied between the active electrode(s) and one or more return electrode(s) such that at least a portion of the nucleus pulposus is ablated, and the volume of the disc""s nucleus pulposus is decreased. After ablation of disc tissue at the first region of the intervertebral disc, other regions of the disc may be contacted with the at least one active electrode for ablation of disc tissue at the other regions of the disc. In one embodiment of the invention, axial translation of the at least one active electrode within the disc while applying the first high frequency voltage, leads to formation of a channel within the treated disc. The diameter of such a channel may be increased by rotating the at least one active electrode about the longitudinal axis of the shaft while applying the first high frequency voltage. Optionally, after a channel has been formed in the disc, disc tissue in the vicinity of the channel may be coagulated, or made necrotic, by applying a second high frequency voltage, wherein the second high frequency voltage may have different parameters as compared with the first high frequency voltage.
In another aspect, the present invention provides a method for treating an intervertebral disc, wherein the method involves providing an electrosurgical system including a probe having a shaft and a handle, the shaft having at least one active electrode located on the distal end portion of the shaft, and wherein the shaft distal end portion includes a pre-defined bias. The method further involves inserting the shaft distal end portion within the disc, and ablating at least a portion of the nucleus pulposus tissue from the disc such that the volume of the disc is decreased with minimal collateral damage to non-target tissue within the disc. The ablating step involves applying a high frequency voltage between the at least one active electrode and at least one return electrode. The high frequency voltage is sufficient to vaporize an electrically conductive fluid (e.g., a gel, isotonic saline, and/or tissue fluid) located between the at least one active electrode and the target tissue. Within the vaporized fluid a plasma is formed, and charged particles (e.g., electrons) are accelerated towards the nucleus pulposus to cause the molecular dissociation of nucleus pulposus tissue at the site to be ablated. This molecular dissociation is accompanied by the volumetric removal of disc tissue at the target site.
In one embodiment, inserting the shaft distal end portion in the disc involves advancing the shaft distal end portion via an introducer needle, the introducer needle having a lumen and a needle distal end, such that when the shaft distal end portion is advanced distally beyond the needle distal end, the at least one active electrode does not make contact with the needle distal end. One or more stages in the treatment or procedure may be performed under fluoroscopy to allow visualization of the shaft within the disc to be treated. Visualization of the shaft may be enhanced by inclusion of a radiopaque tracking device on the distal end of the shaft. The depth of penetration of the shaft into a disc can be monitored by one or more depth markings on the shaft.
In another aspect of the invention, the method further comprises retracting the shaft distal end portion proximally within the lumen of the introducer needle, wherein the at least one active electrode does not make contact with the needle distal end.
In another aspect of the invention, the shaft of the electrosurgical system includes a shield, and a distal insulating collar. In yet another aspect of the invention, the at least one active electrode includes an apical spike and a cusp. Applicants have found that an active electrode having an apical spike and a cusp promotes high current density in the vicinity of the active electrode.
For a further understanding of the nature and advantages of the invention, reference should be made to the following description taken in conjunction with the accompanying drawings.